HOWTO install Oracle Instant Client with MacPorts

In the process of getting a working PHP + Oracle installation going on my Mac, I found out that the MacPorts project has most of the bits already set up for me. Trouble is, the usual way it handles downloads doesn't play nice with Oracle's web site, which expects you to accept a license agreement with your web browser before offering their Instant Client for download.

I had incorrectly reported this as a bug in MacPorts, but Instant Client port maintainer Ryan Schmidt set me right and told me how to install it after downloading the required files in my browser. Not the best solution, but it worked. Thanks Ryan!